Letters testamentary (aka "letters of administration" or "letters of representation") refers to the official document issued by the relevant probate court authorizing the administrator (“executor” if there is a will, or “personal representative” if no will), to take control of a deceased person's estate.
Letters are issued in the context of a probate proceeding, upon petition by the person seeking appointment as administrator. Any one “interested” in the estate may object to the petition by filing written grounds of opposition. Grounds for objection may be the competence of the petitioner, his or her right to letters, or the objector’s allegedly superior right.
Letters are necessary for allow the administrator to obtain control over the decedent’s assets. Letters must be presented to banks and other institutions along with the decedent’s birth certificate.
Letters can be issued to more than one individual, and can be revoked by the probate court upon a later petition filed by an “interested person.”